Leiomyosarcoma of the kidney is a rare entity, and our understanding of this type of renal sarcomas is limited. A 46-year-old Caucasian male presented with a chief complaint of right flank pain for one month. He came to our facility for an additional opinion regarding the management of his renal mass. Computed tomography (CT) of the abdomen showed an enhancing, heterogeneous right renal mass, consistent with the features of renal cell carcinoma (RCC). Robotic-assisted total nephrectomy of the right kidney revealed a tan mass with central necrosis that involved the upper pole of the kidney. Based on gross specimen observation and immunochemical analysis, the patient was diagnosed with high-grade leiomyosarcoma. While the prognosis is poor, radical nephrectomy remains the treatment of choice. The potential benefits of adjuvant therapy should be discussed with selected patients.